A read below the depth that filled the memo re-spells, so the depth guards still run

AGENTS.md

@@ -316,9 +316,12 @@ someone spells it or pins it.
 - The parse keeps each node's readable spelling in a memo, so the `commonMarkSpelling` ask spells a
   node once rather than once per level above it (18). The node reference is the key, which holds
   because the parse builds one object per position; `adfToMarkdown` passes no memo, where a
-  consumer's document may hold one node at two positions (4b). A kept spelling rebases: `text` and
-  `spelling` carry no depth, `headroom` is affine in it, and a reuse sits at or above the depth that
-  filled it. Only what succeeded is kept, so no path minted at another position is ever read.
+  consumer's document may hold one node at two positions (4b). `text` and `spelling` carry no depth
+  and `headroom` is affine in it, so a read above the depth that filled the entry rebases; a read
+  below re-spells, because a hit skips the depth guards the walk it replaces runs and an ordered
+  list past the marker cap gives way, spending two emitter levels where the parser spent one. A
+  give-way is kept too and serves any depth, reading the node's shape alone. Only what succeeded is
+  kept, so no path minted at another position is ever read.
 - No casts: `as`, `as unknown as`, non-null `!`. A boundary owes a type guard validating the
   fields it claims (`isAdfDocument`); past it everything is typed. Make invalid states
   unrepresentable.

src/markdown/emit/adf-to-markdown.ts

@@ -103,8 +103,11 @@ export function commonMarkSpelling(node: AdfNode, path: ConvertErrorPath, depth:
 
 function readableBlock(node: AdfNode, path: ConvertErrorPath, depth: number, memo: SpellingMemo | undefined): Result<EmittedBlock> | undefined {
   const kept = memo?.get(node)
-  // A reuse sits no deeper than the fill it reads, so the kept headroom only ever grows (AGENTS.md §11).
-  if (kept !== undefined) return kept.block === undefined ? undefined : success({ ...kept.block, headroom: kept.block.headroom + kept.depth - depth })
+  if (kept !== undefined) {
+    if (kept.block === undefined) return undefined
+    // A read below the fill would skip the depth guards the walk it replaces runs (AGENTS.md §11).
+    if (depth <= kept.depth) return success({ ...kept.block, headroom: kept.block.headroom + kept.depth - depth })
+  }
   const spelled = spellReadableBlock(node, path, depth, memo)
   if (spelled === undefined) memo?.set(node, { block: undefined, depth })
   else if (spelled.ok) memo?.set(node, { block: spelled.value, depth })

src/markdown/parse/markdown-to-adf.test.ts

@@ -672,7 +672,7 @@ test('refuses input nested deeper than the parser carries', () => {
   assert.equal(code(markdownToAdf(marks(largestNesting + 1))), 'unsupported-nesting-depth')
   assert.deepEqual(content(markdownToAdf(marks(largestNesting))), [{ content: [marked('a', underline)], type: 'paragraph' }])
   const nest = (names: readonly string[], body: string): string => [...names.map((name) => `!adf:${name}\n`), body, ...names.map((name) => `!adf:/${name}\n`).reverse()].join('')
-  const repeated = (name: string): string[] => Array.from({ length: largestNesting }, () => name)
+  const repeated = (name: string, levels: number = largestNesting): string[] => Array.from({ length: levels }, () => name)
   assert.ok(markdownToAdf(nest(repeated('panel'), '!adf:paragraph {localId=a-1}\nPart.\n!adf:/paragraph\n')).ok)
   assert.deepEqual(position(markdownToAdf(nest(['expand', ...repeated('panel'), 'expand'], 'Part.\n'))), { line: 501, offset: 5501 })
   assert.equal(code(markdownToAdf(nest(['panel', ...repeated('expand'), 'panel'], 'Part.\n'))), 'unsupported-nesting-depth')
@@ -680,6 +680,16 @@ test('refuses input nested deeper than the parser carries', () => {
   const directiveLists = largestNesting / 2
   assert.ok(markdownToAdf(listed(directiveLists)).ok)
   assert.equal(code(markdownToAdf(listed(directiveLists + 1))), 'unsupported-nesting-depth')
+  const asking = (body: string): string => `!adf:bulletList\n!adf:listItem\n${body}!adf:/listItem\n!adf:/bulletList\n`
+  // Two items past the largest list marker leave the list no readable spelling, so the emitter
+  // walks it as list plus item where the parser counted one level.
+  const overflowing = (body: string): string => {
+    const marker = '999999999. '
+    return `${marker}${body.replace(/^(?!$)/gm, ' '.repeat(marker.length)).slice(marker.length)}\n${marker}z\n`
+  }
+  const overflowed = (panels: number): string => asking(overflowing(overflowing(asking(`---\n${nest(repeated('panel', panels), 'Part.\n')}`))))
+  assert.equal(code(markdownToAdf(overflowed(493))), 'unsupported-node-shape')
+  assert.equal(code(markdownToAdf(overflowed(494))), 'unsupported-nesting-depth')
   assert.ok(markdownToAdf(`${'- '.repeat(largestNesting)}a\n`).ok)
   assert.equal(code(markdownToAdf(`${'- '.repeat(largestNesting + 1)}a\n`)), 'unsupported-nesting-depth')
 })

todo-history.md

@@ -837,12 +837,17 @@ The done `todo.md` items in full, as they were written. `todo.md` keeps a one-li
       rejected: it reports the outer offender where the build reports the inner one (the
       maintainer, 2026-09-18).
       **Measured** (2026-09-19): the parse keeps each node's readable spelling (AGENTS.md §11), and
-      250 nested directive lists fall from 1.22 s to 0.07 s at 16.1 kB and from 5.20 s to 0.19 s at
-      261 kB; a panel between every pair of lists 1.00 s to 0.07 s, an opaque carry in every item
-      1.08 s to 0.04 s. The two depth-boundary tests are what pin the rebase — dropping it reddens
-      both — so no figure enters the gate (§14), as 4c settled for a behaviour-preserving cost fix.
-      The one list accounting was not taken: 4b settled that accounting the day this was filed, and
-      reopening it is an ask rather than a chunk.
+      250 nested directive lists fall from 1.22 s to 0.04 s at 16.1 kB and from 5.20 s to 0.12 s at
+      261 kB; a panel between every pair of lists 1.00 s to 0.05 s, an opaque carry in every item
+      1.08 s to 0.03 s. No figure enters the gate (§14), as 4c settled for a behaviour-preserving
+      cost fix; what the gate holds is the refusal. The rebase's sign is pinned by the two
+      depth-boundary tests already there, its magnitude by a third case the review found: an ordered
+      list past the marker cap gives way, so the emitter spends two levels where the parser spent
+      one, and two such lists put a read below the depth that filled its entry — which a hit would
+      answer without the depth guards the walk runs, naming a different refusal at a different path.
+      That read re-spells (the stability-reviewer, 2026-09-19). The one list accounting was not
+      taken: 4b settled that accounting the day this was filed, and reopening it is an ask rather
+      than a chunk.
 
 ## 5 — Ship `0.1.0`